Method for reinforcing piling, and piling

ABSTRACT

The purpose of the present invention is to provide a method by which a piling is reinforced and stable support strength can be provided to a building. The method accordingly includes a step for removing a peripheral region of a buried piling, and exposing the piling, and a step for forming in the removed area a reinforcement layer surrounding the piling. Employing a reinforcement method of such description enables load from the building to be supported by the piling and the reinforcement layer. The reinforcement layer can be formed by laying crushed rock, sandbags, concrete, or mortar; pouring a hardening materials; or a combination thereof.

TECHNOLOGICAL FIELD

This invention relates to reinforcement of a foundation of a building, and in particular, relates to reinforcement of a pile of a foundation.

BACKGROUND TECHNOLOGY

When a load of a building increases due to enlargement of the building or the like, when a bearing power is insufficient because of a soft ground, or when a foundation pile deteriorates, it is necessary to reinforce a foundation of the building. Examples of a reinforcement method of the foundation are additional placement of a new pile (additional placement) and methods described in Patent document 1 and Patent document 2. The method described in Patent document 1 inserts a steel pipe into a pile used in a foundation of a building, the steel pipe being smaller than the pile in diameter, thereby reinforcing the pile from inside. The method described in Patent document 2 winds a sheet-like fibrous material around a peripheral surface of a pile to reinforce an outer peripheral surface of the pile.

In the case where the new pile is placed additionally, if a bearing foundation exists at a deep position, a long pile is used correspondingly or relatively short piles are joined and used.

[Patent document 1] JP-A-2004-60155

[Patent document 2] JP-A-2007-138510

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

When the conventional additional placement is executed, it is necessary to dig a wide area of the foundation ground of the building to secure a work space for press-fitting a new pile, thereby complicating the work. A placing space for press-fitting the new pile is necessary. Therefore, the work can be difficult depending on the building as a construction object. Also, it is necessary to prepare the pile long enough to reach the bearing foundation or to join the multiple short piles to achieve the length enough to reach the bearing foundation. In this way, this method is disadvantageous in terms of cost. The method of Patent document 1 or Patent document 2 reinforces a specific point of the pile such as a degraded point. Therefore, the method is not suitable to an object to improve the bearing power of the entire pile.

Even in the case where the new pile is placed additionally, press-fitting the pile long enough to reach the bearing foundation requires a large work amount. Moreover, using the long pile is disadvantageous in terms of cost. Also in the case where the relatively short piles are joined, press-fitting the joined piles to reach the deep bearing foundation requires a large work amount.

Therefore, it is an object of the present invention to provide a method for improving a bearing power of a pile. It is another object of the present invention to provide a method for placing a pile, which exerts a desired bearing power at an intermediate bearing foundation even if the pile is not press-fitted to reach a deep bearing foundation.

MEANS FOR SOLVING THE PROBLEMS

The present invention was invented to solve at least one of the above-mentioned problems. A first aspect of the present invention includes following elements.

A pile reinforcement method, comprising:

a step for removing a peripheral region of a buried pile to expose the pile; and

a step for forming in the removed region a reinforcement layer surrounding the pile.

With the reinforcement method according to the first aspect, the reinforcement layer is formed to surround the exposed pile. Accordingly, the load of the building is borne by the pile and the reinforcement layer. Thus, the length and the thickness required of the pile and/or the press-fitting power can be reduced. The entire work load required for the construction can be reduced although the work to form the reinforcement layer is added.

It is preferable that the reinforcement layer is formed to be even around the exposed pile. In other words, it is preferable that the center of the reinforcement layer coincides with the center of the pile. It is preferable that the reinforcement layer is not fixed to the pile but is brought into contact with the peripheral surface of the pile and that a certain joining force is provided therebetween.

Thickness of the reinforcement layer in the axial direction of the pile (i.e., width in vertical direction) is not limited in particular. For example, the horizontal width of the reinforcement layer may be equal to the vertical width of the reinforcement layer. The thickness of the reinforcement layer may be uniform or may vary continuously or stepwise in the axial direction of the pile. For example, the shape of the reinforcement layer may be a circular column shape, a partial conical shape or a truncated conical shape, whose center coincides with the axis line of the pile.

It is preferable to apply a pressing force to the reinforcement layer when the reinforcement layer is formed around the pile. Thus, the ground around the reinforcement layer is packed and strengthened. In addition, a sufficient joining force can be provided to the reinforcement layer and the pile. As a result, a force is applied to the pile and the buried state of the pile stabilizes.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 is a schematic diagram showing a pile reinforcement method 1.

[FIG. 2] FIG. 2 is a diagram explaining effects of a pile 20 reinforced by the pile reinforcement method 1.

[FIG. 3] FIG. 3 is a schematic diagram showing a pile reinforcement method 100.

[FIG. 4] FIG. 4 is a diagram explaining effects of a pile 20 reinforced by the pile reinforcement method 100.

[FIG. 5] FIG. 5 is a schematic diagram showing a pile reinforcement method 101.

[FIG. 6] FIG. 6 is a schematic diagram showing a pile reinforcement method 102.

[FIG. 7] FIG. 7 is a diagram explaining effects of a pile 20 reinforced by the pile reinforcement method 102.

[FIG. 8] FIG. 8 is a schematic diagram showing a placement method of a pile 200.

[FIG. 9] FIG. 9A is a perspective view showing a pile 200 attached with a coupling member 600, and FIG. 9B is a perspective view showing a pile 202 attached with a flange member 630.

[FIG. 10] FIG. 10 is a schematic diagram explaining an embodiment example according to another aspect of the present invention.

[FIG. 11] FIG. 11 is a schematic diagram explaining effects of a stabilizing member 80.

[FIG. 12] FIG. 12 is a schematic diagram explaining a modification example of another aspect of the present invention.

[FIG. 13] FIG. 13 is a schematic diagram explaining another modification example of another aspect of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In a pile reinforcement method according to a first aspect of the present invention, first, a peripheral region of a buried pile is removed to expose the pile (first step). In the first step, an area of the removed region is not limited in particular but may be decided arbitrarily in consideration of a necessary bearing power, a size of a flange member (described later), hardness of a ground around the pile and the like. For example, the removed region may be a region having the shape of a circular column or a rectangular column, whose central axis coincides with an axis line of the pile. The method for removing the peripheral region of the pile is not limited in particular as long as the method can form an empty space in the peripheral region of the pile. For example, the peripheral region of the pile may be dug down to remove soil, sand and the like. Alternatively, compaction of a ground in the peripheral region may be performed to form the empty space and expose the pile.

According to the pile reinforcement method according to the first aspect of the present invention, the peripheral region of the pile is removed to expose the pile, and then a reinforcement layer is formed around the pile. More specifically, the reinforcement layer is formed from a bottom of the removed region (second step). Thus, a hard layer is formed in the peripheral region of the pile. For example, as the method for forming the reinforcement layer, a method of laying crushed stones, sandbags, concrete or mortar or a method of pouring in a solidification agent may be employed or a method combining them may be employed. When the crushed stones, the sandbags, the concrete or the mortar is laid, laying thickness may be decided arbitrarily in consideration of the required bearing power, the hardness of the ground around the pile and the like. When the solidification agent is used, a publicly-known solidification agent may be adopted. It is preferable that the reinforcement layer is formed such that its top surface is horizontal.

The type of the pile according to the first aspect is not limited in particular. For example, the pile reinforcement method according to the first aspect may be applied to well-known piles such as a steel pipe pile, a PHC pile, an RC pile and an SC pile.

A flange member may be attached to the exposed pile (third step).

If the flange is provided, the flange member contacting the reinforcement layer is attached to the buried pile. Accordingly, a bearing power can be obtained from the reinforcement layer through the flange member, and the bearing power of the entire pile improves. Unlike the case where the additional placement of the pile is performed, no space for the additional placement is necessary. Moreover, a construction area is limited to the peripheral region of the pile. Therefore, construction can be performed easily for a building, for which a sufficient work space cannot be secured. Also, the small construction area contributes to reduction of a construction period. A predetermined bearing power can be obtained at an intermediate bearing foundation even without press-fitting the pile until the pile reaches a deep bearing foundation. Therefore, a relatively short pile may be used.

It is desirable that the flange member has a shape with a sufficient area to contact the reinforcement layer. For example, a disc-like shape, a rectangular plate-like shape, a hexagonal plate-like shape or the like, whose center coincides with the axis line of the pile, may be employed. It is desirable that the flange member has a shape symmetrical around the axis line of the pile because the load of the building is loaded on the flange member in a preferable balance. The flange member may be formed by combining multiple plate-like members.

The method for attaching the flange member to the pile is not limited in particular. For example, welding, adhesion with an adhesive, joining with a bolt, fitting with a fitting mechanism, thread connection with a thread mechanism provided by threading or the like may be employed. A connection member connectable with the flange member and the pile may be prepared, and the flange member may be attached to the pile through the connection member.

The flange member that contacts the reinforcement layer need not necessarily contact the reinforcement layer when the flange member is attached to the pile or when the construction is completed. In other words, there may be a gap between the reinforcement layer and the flange member when the flange member is attached to the pile or when the construction is completed. The soil and the like backfilled after the completion of the construction get into the gap and fill the gap. Alternatively, the pile and the flange member are press-fitted by the load of the building, so the gap is compressed and the flange member contacts the reinforcement layer. Thus, the bearing power against the load of the building is obtained from the reinforcement layer through the flange member.

After the flange member is attached to the pile such that the flange member contacts the reinforcement layer, the material for forming the reinforcement layer may be laid or poured in again to cover the flange member. Thus, the flange member is placed in the reinforcement layer. As a result, the contact area between the reinforcement layer and the flange member increases and the bearing power improves as a whole. Since the flange member is placed in the reinforcement layer, displacement of the flange member with respect to the reinforcement layer after the construction can be prevented.

According to another aspect of the present invention, a pile is buried in a ground, in which a reinforcement layer is formed near a surface of the ground. The pile has a flange member provided to stand on a pile head or a peripheral surface of the pile. The flange member contacts the reinforcement layer when the pile is buried in the ground. The reinforcement layer can be formed by a method of digging the ground and laying crushed stones, sandbags, concrete or mortar or pouring in a solidification agent or a method combining them. With the pile according to the aspect, the flange member contacts the reinforcement layer and therefore the bearing power improves. Accordingly, a predetermined bearing power can be obtained at an intermediate bearing foundation even without press-fitting the pile until the pile reaches a deep bearing foundation. As a result, the pile length may be reduced.

It is desirable that the flange member has a shape with a sufficient area to contact the reinforcement layer. For example, a disc-like shape, a rectangular plate-like shape, a hexagonal plate-like shape or the like, whose center coincides with the axis line of the pile, may be employed. It is desirable that the flange member has a shape symmetrical around the axis line of the pile because the load of the building borne by the pile is loaded on the flange member in a preferable balance.

In the case where the flange member is provided on the peripheral surface of the pile, the position for providing the flange member may be determined arbitrarily in consideration of the depth and the hardness of the bearing foundation, on which the pile is placed, and the hardness and the composition of the reinforcement layer. It is preferable that the flange member surrounds the peripheral surface of the pile because the bearing power can be obtained in a preferable balance and deviation of the axis can be prevented. It is preferable that the flange member is provided perpendicularly to the peripheral surface of the pile. It is because the bearing power obtained with the flange member is directed in the vertical direction and the bearing power can be exerted effectively to the building or the like, which the pile bears.

A distance from the connection between the flange member and the pile to an outer edge of the flange member (i.e., size of flange member) may be approximately 0.5 to approximately 5.0 times (or more preferably, approximately 1.0 to approximately 3.0 times) larger than the diameter of the pile. By thus setting the size of the flange member, a sufficient bearing power can be obtained. The type of the pile according to the second aspect is not limited in particular like the first aspect. For example, piles such as a steel pipe pile, a PHC pile, an RC pile and an SC pile may be employed.

Hereafter, embodiments of the present invention will be explained in greater details.

First Embodiment

FIG. 1 is a schematic diagram showing a pile reinforcement method 1 according to the present invention. The pile reinforcement method 1 removes soil in a peripheral region of a pile head 21 of a pile 20, which is buried in a ground 10 as a foundation of a building (not shown). Thus, as shown in FIG. 1A, an empty space 40 is formed and the pile 20 is exposed. The empty space 40 is formed in a cylindrical shape, whose central axis coincides with the pile 20 and which is approximately 500 mm in diameter and approximately 1000 mm in depth. A bottom 41 of the space 40 is substantially a horizontal surface.

Then, as shown in FIG. 1B, a reinforcement layer 51 is formed by laying crushed stones 50 on the bottom 41 of the empty space 40. Thickness of the reinforcement layer 51 is approximately 500 mm. The crushed stones 50 are laid densely, and a top surface of the reinforcement layer 51 is horizontal. It is preferable to apply a pressing force to the crushed stones 50 when laying the crushed stones 50. For example, it is preferable to put the crushed stones 50 into the empty space 40 in several times and to pack them each time the crushed stones 50 are put in. By performing the packing work in several times, the reinforcement layer can be made stronger. In addition, even in the case where sufficient width of an opening of the empty space 40 cannot be secured or in the case where a large force cannot be applied to the reinforcement layer at once in a narrow work space under the floor or the like, the reinforcement layer can be packed sufficiently. As a result, the ground around the reinforcement layer is strengthened and the buried state of the pile is stabilized more.

A surface 52 of the reinforcement layer 51 facing the pile 20 contacts an outer peripheral surface 24 of the pile 20. Then, as shown in FIG. 1C, the empty space 40 is filled back to complete the construction. The entirety of the empty space 40 may be filled with the crushed stones 50 to serve as the reinforcement layer.

FIG. 2 is a diagram explaining effects of the pile reinforcement method 1. As shown in FIG. 2, in the pile reinforcement method 1, the crushed stones are packed to serve as the reinforcement layer 51. Therefore, a high frictional coefficient can be obtained between the reinforcement layer 51 and the pile 20. With the reinforcement layer 51 providing the high frictional coefficient, a bearing power Pa is provided by a load F A frictional force is generated by the load F also in a connection between the outer peripheral surface 24 of the pile 20 and the ground 10, thereby providing a bearing power Pb. Thus, a bearing power P₁ opposing the load F₁ is obtained from the bearing foundation 11 at the tip 23 of the pile 20, and the bearing powers Pa, Pb are obtained at the outer peripheral surface 24 of the pile 20.

A force from the footing 30 acts on also the reinforcement layer 51, so the load of the building is borne also by the reinforcement layer 51.

The construction area of the pile reinforcement method 1 is only in the peripheral region of the pile 20. Therefore, a small working space will suffice. Thus, the method can be applied to a building, for which a sufficient working space cannot be secured. Since the working space is small, the construction period can be reduced.

In the present embodiment, the reinforcement layer 51 is formed by laying the crushed stones 50. Alternatively, the reinforcement layer 51 may be formed by laying sandbags, concrete or mortar. Alternatively, the reinforcement layer 51 may be formed by pouring in a solidification agent.

In the example shown in FIGS. 1 and 2, the reinforcement layer 51 is buried in the ground. Alternatively, a surface of the reinforcement layer 51 may be exposed.

Second Embodiment

FIG. 3 is a schematic diagram showing a pile reinforcement method 100 according to the present invention. Members similar to the members shown in FIGS. 1 and 2 are denoted with the same signs as FIGS. 1 and 2 and explanation thereof is omitted. The pile reinforcement method 1′ forms the empty space 40 as in the pile reinforcement method 1 shown in FIGS. 1 and 2 to expose the pile 20 (refer to FIG. 3A). Then, as shown in FIG. 3B, the crushed stones 50 are laid on the bottom 41 of the empty space 40 to form the reinforcement layer 51. The thickness of the reinforcement layer 50 is approximately 500 mm. The crushed stones 50 are laid densely, and the top surface of the reinforcement layer 51 is horizontal. Then, a flange member 60 is attached to the pile 20 such that the flange member 60 contacts the reinforcement layer 51 as shown in FIG. 3C. The flange member 60 has a disc-like shape, whose center coincides with the axis line of the pile 20, and has an outer diameter of approximately 300 mm. Then, as shown in FIG. 3D, the empty space 40 is filled back to complete the construction.

FIG. 4 is a diagram explaining effects of the pile reinforcement method 100. As shown in FIG. 4, in the pile reinforcement method 100, the flange member 60 attached to the pile 20 contacts the top surface of the reinforcement layer 51 formed by laying the crushed stones 50. Thus, if the load F of the building acts on the pile 20, a part F₁ of the load F acts on the bearing foundation 11 from the tip 23 of the pile 20 and another part F₂ of the load F acts on the top surface of the reinforcement layer 51 from the flange member 60. Thus, a bearing power P₁ opposing the load F₁ is obtained from the bearing foundation 11, and a bearing power P₂ opposing the load F₂ is obtained from the top surface of the reinforcement layer 51. Also, a bearing power P₃ generated by a frictional force between the outer peripheral surface 24 of the pile 20 and the ground 10 is obtained. In this way, the pile reinforced by the pile reinforcement method 100 provides the additional supporting force P₂, so the bearing power of the pile 20 improves.

The construction space of the pile reinforcement method 100 is only the peripheral region of the pile 20. Therefore, the small working space will suffice. Thus, the method can be easily applied to a building, for which a sufficient working space cannot be secured. Since the working space is small, the construction period can be reduced.

Third Embodiment

FIG. 5 is a schematic diagram showing a pile reinforcement method 101 according to another embodiment of the present invention. Members similar to the members shown in FIGS. 1 to 4 are denoted with the same signs as FIGS. 1 to 4 and explanation thereof is omitted. As in the pile reinforcement method 100 shown in FIGS. 3A to 3C, the pile reinforcement method 101 forms the empty space 40 to expose the pile 20, lays the crushed stones 50 on the bottom 41 of the empty space 40 to form the reinforcement layer 51, and attaches the flange member 60 to the pile 20 (refer to FIGS. 5A to 5C). Then, as shown in FIG. 5D, the crushed stones 50 are laid in the empty space 40 further to cover the flange member 60. Thus, the flange member 60 is placed in the reinforcement layer 51. After that, the empty space 40 is filled back to complete the construction as shown in FIG. 5E.

The pile reinforcement method 101 exerts effects similar to those of the pile reinforcement method 100. Furthermore, since the flange member 60 is placed in the reinforcement layer 51, the contacting area between the flange member 60 and the reinforcement layer 51 increases, so the total amount of the frictional force caused by the load F increases. Thus, the pile reinforcement method 101 contributes to the improvement of the bearing power against the load F as a whole. Since the flange member 60 is placed in the reinforcement layer 51, occurrence of displacement of the flange member 60 with respect to the reinforcement layer 51 after the construction can be prevented.

Fourth Embodiment

FIG. 6 is a schematic diagram showing a pile reinforcement method 102 according to another embodiment of the present invention. Members similar to the members shown in FIGS. 1 to 4 are denoted with the same signs as FIGS. 1 to 4 and explanation thereof is omitted. As in the pile reinforcement method 100 shown in FIGS. 3A to 3C, the pile reinforcement method 102 forms the empty space 40 to expose the pile 20 and lays the crushed stones 50 on the bottom 41 of the empty space 40 to form the reinforcement layer 51 (refer to FIGS. 6A and 6B). Then, as shown in FIG. 6C, the flange member 60 is attached to the pile 20 at a position distanced from a top surface of the reinforcement layer 51 by a certain distance. Then, as shown in FIG. 6D, the empty space 40 is filled back to complete the construction. Thus, the flange member 60 and the reinforcement layer 61 are distanced from each other by a certain distance and a gap 70 exists when the construction is completed.

FIG. 7 is a diagram explaining effects of the pile reinforcement method 102. In the pile reinforcement method 102, the gap 70 exists as shown in FIG. 6D when the construction is completed. If a load F is applied to the pile 20, the pile 20 and the flange 60 are press-fitted gradually, and the flange member 60 contacts the top surface of the reinforcement layer 51. That is, the gap 70 substantially disappears. Thus, a bearing power opposing the load F is obtained like the pile reinforcement method 100. In this way, there is no need to bring the flange member 60 into contact with the top surface of the reinforcement layer 51 during the construction or when the construction is completed. Accordingly, the work space can be secured easily during the attaching work of the flange member 60 and the attaching workability improves.

Fifth Embodiment

FIG. 8 is a schematic diagram showing a method for placing a pile 200 according to another embodiment of the present invention. As shown in FIG. 8A, the pile 200 is press-fitted into a bottom 401 of a recess 400 formed by digging the ground. The shape of the recess 400 is a circular column-like shape with a diameter of approximately 500 mm and depth of approximately 1000 mm. The bottom 401 is a substantially horizontal surface.

FIG. 9A is a perspective view showing the pile 200. The pile 200 is approximately 100 mm in diameter and approximately 1500 mm in length. A coupling member 600 is attached to a pile head by welding beforehand in a factory. The coupling member 600 has a flange part 601, a first joint 602 and a second joint 603. The flange part 601 has a disc-like shape with a diameter of approximately 300 mm. A distance d from a connection 604 between the flange part 601 and the pile 200 to an outer edge 605 of the flange part 601 is approximately 100 mm. An outer diameter of each of the first joint 602 and the second joint 603 is approximately 90 mm and is slightly shorter than an inner diameter of the pile 200. Height of each of the first joint 602 and the second joint 603 is approximately 100 mm. The first joint 602 is inserted into the pile head of the pile 200. The coupling member 600 and the pile 200 are joined by welding in the factory.

Then, as shown in FIG. 8B, the crushed stones 50 are laid on the bottom 401 of the empty space 400 to form the reinforcement layer 51 in a peripheral region of the pile 200. Thickness of the reinforcement layer 51 is approximately 500 mm. The crushed stones 50 are laid densely, and the top surface of the reinforcement layer 51 is horizontal. Then, as shown in FIG. 8C, the pile 200 is press-fitted so that the flange part 601 contacts the reinforcement layer 51. A pile 201 is placed such that the second joint 603 of the coupling member 600 is inserted into a lower end of the pile 201. The coupling member 600 and the pile 201 are welded and fixed. Then, as shown in FIG. 8D, the recess 400 is filled back to complete the construction.

With the pile 200 of the present embodiment, the bearing power can be obtained from the reinforcement layer 51 with the use of the flange part 601 of the coupling member 600, so the bearing power of the entire pile improves. Therefore, a predetermined bearing power can be obtained even without press-fitting the pile 200 to the deep bearing foundation. The flange part 601 has the disc-like shape, whose center coincides with the axis line of the pile 200. Therefore, the load of the building or the like borne by the pile 200 is loaded on the flange part 601 in a preferable balance, so the occurrence of the deviation of the axis can be prevented. In the present embodiment, the pile 200 and the pile 201 are used. Alternatively, a third pile, a fourth pile and further piles may be joined in series through the coupling members 600 and used in accordance with the depth to press-fit the piles.

In the present embodiment, the pile 200 attached with the coupling member 600 having the flange part 601 is used. Alternatively, a pile 202 having a flange member 630 provided on a peripheral surface 203 near the pile head as shown in FIG. 9B may be used. An outline of the flange member 630 is the same as the flange part 601. The flange member 630 has a hole 631 at its center, the hole 631 being slightly larger than the diameter of the pile 202. An edge 631 a of the hole 631 and a peripheral surface 203 of the pile 202 near the pile head are joined beforehand by welding in the factory in a state where the pile 202 is fitted in the hole 631. Also with such the pile 202, by bringing the flange member 630 into contact with the reinforcement layer 51, the bearing power of the pile 202 can be improved, so a predetermined bearing power can be obtained even without press-fitting the pile 202 to the deep bearing foundation. Therefore, the length of the pile 202 can be reduced.

A cylindrical member may be formed from the peripheral portion of the flange member or proximity of the peripheral portion in the press-fitting direction. Effects of the cylindrical member will be explained with a following embodiment. The cylindrical member may be continuous or discontinuous in a circumferential direction.

Sixth Embodiment

A construction method of a foundation using a stabilizing member as an embodiment according to another aspect of the present invention will be explained with reference to FIG. 10.

First, a steel pipe pile 20 is press-fitted into a ground 10 to a predetermined depth such that a pile head 21 of the steel pipe pile 20 substantially coincides with a ground surface (FIG. 10(A)). Then, a circumferential position of a circle having a diameter of approximately 1000 mm centering on an axis line of the steel pipe pile 20 on the ground surface is dug to form a cylindrical recess 81 of approximately 100 mm in width and approximately 500 mm in depth (FIG. 10(B)).

Then, a stabilizing member 80 is placed. The stabilizing member 80 has a flat plate portion 82, which has a disc-like shape with a diameter of approximately 1000 mm, and a side wall portion 83, which has a height of approximately 500 mm and which is provided to stand on the flat plate portion 82 perpendicularly along the entire circumference of the outer periphery of the flat plate portion 82. That is, the stabilizing member 80 is formed in the shape of a cylindrical cup. An inside surface of the cup-like shape of the flat plate portion 82 of the stabilizing member 80 (i.e., inside flat plate surface 82 a) contacts the pile head 21 of the steel pipe pile 20, and the side wall portion 83 of the stabilizing member 80 is fitted into the recess 81. Thus, the stabilizing member 80 is placed to cover the pile head 21 of the steel pipe pile 20.

Then, a footing 30 of a building is brought into contact with a surface of the flat plate portion 82 of the stabilizing member 80 opposite from the inside flat plate surface 82 a (i.e., outside flat plate portion 82 b), whereby a foundation of the building is constructed. The flat plate portion 82 of the stabilizing member 80 is larger than a bottom surface of the footing 30. Substantially an entire area of the bottom surface of the footing 30 contacts the outside flat plate surface 82 b of the flat plate portion 82.

Effects of the stabilizing member 80 will be explained with reference to FIG. 11. If a load F of the building acts on the stabilizing member 80, a part Fa of the load F acts on a bearing foundation 11 from a tip 23 of the steel pipe pile 20 through the stabilizing member 80, and another part Fb of the load F acts on the ground 10 from the inside flat plate portion 82 a and the side wall portion 83 of the stabilizing member 80. Thus, a bearing power Pa opposing the load Fa is obtained from the bearing foundation 11. Further, a bearing power Pb opposing the load Fb is obtained from the inside flat plate portion 82 a, and a bearing power Pc opposing the load Fb is obtained from the bottom surface of the side wall portion 83. Moreover, soil in a region surrounded by the side wall portion 83 of the stabilizing member 80 and the steel pipe pile 20 is bound by the side wall portion 83 and the steel pipe pile 20. Therefore, a reaction force Pd is obtained against the load Fb. Also, a bearing power Pe caused by a frictional force in contacting sections, at which the wall surface of the side wall portion 83 of the stabilizing member 80 and the outer peripheral surface 24 of the steel pipe pile 20 contact the ground 10, is obtained. In this way, the bearing powers Pa to Pe are obtained by the stabilizing member 80, whereby a large bearing power can be obtained as a whole.

In the sixth embodiment, the flat plate portion 82 of the stabilizing member 80 is larger than the bottom surface of the footing 30, but the present invention is not limited thereto. For example, a stabilizing member 800 having a flat plate portion 820 smaller than the bottom surface of the footing 30 as in a modification example shown in FIG. 12 also exerts effects similar to those of the stabilizing member 80.

In the sixth embodiment, the stabilizing member 80 is provided to cover the pile head 21 of the steel pipe pile 20, but the present invention is not limited thereto. For example, as shown in FIG. 13, a stabilizing member 801 having a through hole 84, through which the steel pipe pile 20 penetrates, in the flat plate portion 82 of the stabilizing member 80 may be used. An area around the steel pipe pile 20 press-fitted into the ground 10 is dug to a predetermined depth to expose an outer peripheral surface of the steel pipe pile. Then, the stabilizing member 801 is attached to the steel pipe pile 20 by welding or the like so that the steel pipe pile 20 penetrates through the through hole 84 of the stabilizing member 801. Then, the soil is filled back together with a solidification agent to the pile head 23 of the steel pipe pile 20 to form a solidified layer 12. Then, the footing 30 is brought into contact with the pile head 21 of the steel pipe pile 20. The stabilizing member 801 placed in this way also exerts effects similar to the effects of the stabilizing member 80.

In the sixth embodiment, the flat plate portion 82 of the stabilizing member 80 has the disc-like shape, but the present invention is not limited thereto. Alternatively, the shape of the flat plate portion 82 may be a rectangular shape, a hexagonal shape, other polygonal shapes, an oval shape or a shape combining them. The side wall portion 83 of the stabilizing member 80 is provided to be perpendicular to the flat plate portion 82, but the present invention is not limited thereto. For example, a part or entirety of the side wall portion 83 of the stabilizing member 80 may be slanted with respect to the flat plate portion 82.

The present invention is not limited to the above explanation of the embodiments. Various modifications that can be easily thought of by a person skilled in the art without departing from the scope of description of claims are included in the present invention.

Explanation of Reference Numerals

-   1, 100, 101, 102 Pile reinforcement method -   10 Ground -   20, 200, 201, 202 Pile -   21, 210 Pile head -   23 Tip -   30 Footing -   40 Empty space -   400 Recess -   41, 410 Bottom -   50 Crushed stones -   51 Reinforcement layer -   60, 630 Flange member -   600 Coupling member -   601 Flange part 

1. A pile reinforcement method, comprising: a step for removing a peripheral region of a buried pile to expose the pile, and a step for forming in the removed region a reinforcement layer surrounding the pile.
 2. The pile reinforcement method according to claim 1, wherein the reinforcement layer is formed by laying crushed stones, sandbags, concrete or mortar or by pouring in a solidification agent.
 3. The pile reinforcement method according to claim 1, further comprising: a step for attaching a flange member to the exposed pile, wherein the step for forming the reinforcement layer brings the reinforcement layer into contact with the flange member.
 4. A pile buried in a ground, in which a reinforcement layer is provided near a surface of the ground, the pile comprising: a flange member that is provided to stand on a pile head or a peripheral surface of the pile and that contacts the reinforcement layer when the pile is buried in the ground.
 5. The pile according to claim 4, wherein the flange member is provided to surround the peripheral surface of the pile.
 6. The pile according to claim 4, wherein the flange member is provided to be perpendicular to the peripheral surface of the pile.
 7. The pile according to any one of claim 4, wherein a distance from a connection between the flange member and the pile to an outer edge of the flange member is 0.5 to 5.0 times larger than a diameter of the pile.
 8. The method according to claim 1, wherein the step for forming the reinforcement layer includes: a first crushed stone putting-in step for putting in crushed stones into the removed region, and a first immobilizing step for packing the crushed stones put in by the first crushed stone putting-in step.
 9. The method according to claim 8, wherein the step for forming the reinforcement layer further includes: a second crushed stone putting-in step for putting in crushed stones further on the crushed stones packed by the first immobilizing step; and a second immobilizing step for packing the crushed stones put in by the second crushed stone putting-in step. 